Coolant jackets in both the engine block and the cylinder head have been developed to remove heat from the engine to improve engine operation. EP 0 038 556 B1, for example, describes a cooling system for an internal combustion engine. A first pump is configured to flow coolant through a cylinder head cooling jacket. A second pump is configured to flow coolant through the engine block coolant jacket. The two cooling jackets do not have any connection within the internal combustion engine, but are both fluidly coupled to an outlet conduit in a main cooling circuit. A cooler bypass conduit branches off from the main cooling circuit. The cooler bypass conduit is fluidly coupled to an inlet in both the cylinder head coolant jacket and the engine block coolant jacket. A control valve in the main cooling circuit is configured to selectively inhibit coolant flow to a cooler in the main cooling circuit and selectively permit coolant flow through the cooler bypass conduit. Additionally, a second control valve is configured to selectively permit coolant flow into the engine block coolant jacket.
However, using two pumps to control the coolant flow in the engine block coolant jacket and cylinder head coolant jacket may increase the cost, weight, and bulkiness of the engine.
Therefore, in some engines coolant jackets in the engine block and the cylinder head may be fluidly separated and coupled to a single pump. In other words, coolant may flow through the coolant jackets in a parallel flow configuration. This arrangement may be referred to as a split cooling design. In this way, the cylinder head, which is thermally coupled primarily to the combustion chamber wall and the exhaust conduits, and the engine block, which is thermally coupled primarily to the friction points, can be cooled differently. The aim of the split cooling design is to provide cooling to the cylinder head and inhibit cooling of the engine block during a warm-up phase. In this way, the engine block can be brought up to the required operating temperature more quickly during start-up.
For example, EP 1 900 919 A1, discloses a split coolant circuit of an internal combustion engine, with a cylinder head coolant jacket and an engine block coolant jacket are provided. The split coolant circuit further includes a pump, a cooler, a thermostat and a heating arrangement, and with a coolant circulating in the split coolant circuit. The thermostat is arranged so as to control the flow of the coolant both through the engine block coolant jacket and through the cooler when the coolant exceeds a predefined temperature.
When a split cooling circuit is utilized in an internal combustion engine, friction losses in the warm-up phase can be reduced. However, the split coolant design also heats the engine oil, the coolant, and/or the surfaces of the piston skirts more quickly. Thus, coolant flow strategies have been developed to substantially inhibit coolant flow through the engine block coolant jacket for an extended duration to reduce friction losses during the warm-up phase, in particular after a cold start of the internal combustion engine. This type of coolant flow strategy may be referred to as a “no-flow strategy” for the engine block coolant jacket.
However, vapor may develop in the engine block coolant jacket which may increase temperature variability within the engine block when a “no-flow strategy” is utilized. As a result the engine block may experience thermal degradation. To combat this thermal degradation, coolant may be flowed into the engine block coolant jacket prematurely to reduce the likelihood of engine block degradation.
For example, some engine may include an internal connection between the engine block coolant jacket and the cylinder head coolant jacket such that coolant vapor, formed in the engine block coolant jacket when flow is substantially inhibited in the jacket, can be conducted into the cylinder head coolant jacket, preferably into an inlet-side head coolant jacket. By discharging the hot gases (these naturally collect at an upper region), the no-flow strategy for the engine block coolant jacket can be maintained for longer, because said regions in which hot vapors otherwise accumulate can be traversed by coolant, such that the likelihood thermal damage in said regions is advantageously reduced.
Furthermore, in the case of the no-flow strategy for the engine block coolant jacket, or in the case of the split cooling concept, a situation may arise in which the amount of heat in the cooling circuit cannot meet the heating demands (e.g., cabin heating, window defrost, etc.) in the vehicle.
Furthermore, turbochargers have a turbine and a compressor, with the turbine being driven by means of the exhaust-gas flows such that the compressor side can produce compressed air which is supplied to the internal combustion engine. The turbine may experience thermal loading during engine operation which may lead to thermal degradation of the turbine. Therefore, the turbine housing may be produced from a high-alloyed cast steel in order to withstand the high temperature loadings of the exhaust gases. However, the cast steel is very expensive to produce in particular on account of its alloy elements, for example 37 weight percentage of nickel. Moreover, cast steel is not only expensive but also has a relatively high weight with any additional weight having an adverse effect on the fuel consumption of the motor vehicle as a whole.